A number of arrangements of multipolar medical electrodes for attachment to a patient's skin for deriving electrical signals associated with physiological activity are known in the prior art. Electrodes intended for one-time patient use are considered disposable, while those that can be reused many times are considered permanent.
Conventional permanent medical electrodes are available in several styles, but are generally relatively expensive, must be cleaned carefully between uses, are not self-adhesive, and require an application of electrolytic gel or fluid at the time of each use. Such a permanent multipolar medical electrode is described U.S. Pat. No. 4,082,087 to Howson.
Further, there are a number of single-poled medical electrodes known in the prior art. In order to derive a differential electrical signal, it is typical to use three electrodes. This can be expensive, time consuming, and can lead to electromagnetic interference from the loop formed by the electrode leads, as well as to interaction with electrosurgical equipment. Such a single-poled disposable medical electrode is provided in U.S. Pat. No. 4,126,126 to Bare, et al.
It is desirable that a medical electrode conform well to the skin to provide maximum electrical contact, allow longer wearing time, and ensure patient comfort. Flexible pads of various shapes and configurations have been used to attain conformity with the skin. One such configuration is provided in the above-mentioned Howson patent.
It is also desirable that connections to the electrode be clean, safe, and easily made. For instance, exposed connector prongs can become contaminated by contact with human hands or otherwise, causing a poor electrical connection. If such exposed prongs are pointed, as they often are, there remains a danger of accidentally puncturing the skin of both the technician and the patient. Ease and sureness of connection are also important in the setting in which the electrodes are typically used.